Best Management Practices for Phosphorus in the Environment

Phosphorus is a naturally occurring element, essential to life. It is a vital component of the genetic material found in all cells and is involved in energy transfer reactions. In many soils and aquatic systems, phosphorus is the element that limits growth. When phosphorus is supplied, plant growth is stimulated. In most agricultural situations, additional phosphorus will improve productivity. But in rivers, streams and lakes, phosphorus can cause problems by stimulating excess plant growth and reducing the quality of the water. Like many other things, too much of a good thing can be bad.

Phosphorus in WaterAs with unfertilized soils, phosphorus is often the limiting nutrient in aquatic systems. Unlike soils, aquatic systems have a low buffering capacity or ability to store phosphorus when it increases above natural background levels. If phosphorus is applied to a source of water where it is limiting, the growth of algae and other aquatic micro-organisms will be quickly stimulated. Increased growth requires more oxygen. Growth will continue until either the oxygen or phosphorus becomes limited. If oxygen becomes depleted, all the oxygen-requiring or aerobic organisms in the ecosystem will be affected. If the rate of death of these organisms increases, the oxygen demand in the system will increase even more. Increased rates of death will result in increased demand for oxygen needed for decomposition, until it eventually becomes limiting. When this happens, the system changes from being an oxygen-based to a non-oxygen based or anaerobic system. Under anaerobic conditions, even more changes occur and unpleasant odors are produced. This whole process is know as eutrophication.